Dehydrochlorination of poly(vinyl chloride) with Ca(OH)2 in ethylene glycol and the effect of ball milling

The dehydrochlorination behavior of pure and flexible PVC in ethylene glycol was studied in the presence of Ca(OH)2 at temperatures between 170 °C and 190 °C. Although the dehydrochlorination proceeded slower in Ca(OH)2 than in NaOH, similar dehydrochlorination yields were obtained. It was assumed that the slower reaction rate was a result of the low solubility of Ca(OH)2 and the larger solvation shell of the Ca2+ ion. The dehydrochlorination rate and yield were improved by employing a ball mill. Additionally, diisononyl phthalate and CaCO3 were quantitatively separated from flexible PVC during the ball-milling process. The maximum dehydrochlorination yield of pure PVC after 7 h at 190 °C was 74%. After 8 h at the same temperature, a comparable dehydrochlorination yield of 77% was achieved for flexible PVC, which could be increased by ball milling to 86%.